Technical Field
The present invention relates to electron beam equipment that performs inspection and measurement using an electron beam.
Background Art
Electron beam equipment, such as a scanning electron microscope (SEM) that is used for observation, inspection, or measurement of a sample using an electron beam, accelerates electrons emitted from an electron source and focuses the accelerated electrons on the surface of a sample using an electrostatic lens or a magnetic lens, thereby irradiating the sample surface with the electrons. Such electrons are referred to as primary electrons. Upon irradiation of the sample surface with the primary electrons, secondary electrons (i.e., electrons with low energy and electrons with high energy may also be distinctively referred to as secondary electrons and reflective electrons, respectively) are emitted. When such secondary electrons are detected by scanning the sample surface while deflecting an electron beam, it is possible to obtain a fine pattern on the sample or a scan image of a composition distribution. In addition, when electrons absorbed by the sample are detected, it is also possible to form an absorption current image.
One of the basic performances of a scanning electron microscope is the resolution of an electron beam. Various methods have been attempted to be used to improve the resolution of an electron beam. Among them is a technique of reducing the energy distribution of an electron beam using an energy filter. Such a technique can improve the resolution by reducing the energy distribution and thus reducing chromatic aberrations. Among energy filters, a filer called “Wien filter” is known as a scheme that uses an electron beam in a linear manner. A Wien filter is adapted to generate deflection chromatic aberrations by superimposing a magnetic deflector with an electrostatic deflector (also referred to as ExB), and combining the ExB with a slit on the lower stage to selectively pass an electron beam of partial energy. Wien filters have been mainly used to improve the energy resolution of analytical microscopes so far, and have a possibility of, when applied to reduce chromatic aberrations of an electron lens, being able to improve the resolution of an electron beam probe. Conventional Wien filters are formed by arranging a slit at a position immediately below a combination of a magnetic deflector and an electrostatic deflector (i.e., ExB).